Data storage systems commonly employ replication technologies for protecting the data they store. Conventional replication solutions include continuous replication solutions and snapshot shipping solutions. Continuous replication solutions operate on storage volumes, e.g., LUNs (Logical Unit Numbers), using Fibre Channel or iSCSI (Internet Small Computer System Interface), whereas snapshot shipping solutions operate on file systems and files, e.g., using NFS (Network File System), CIFS (Common Internet File System), or SMB 3.0 (Server Message Block).
A well-known solution for continuous replication is the RecoverPoint system available from EMC Corporation of Hopkinton, Mass. RecoverPoint systems include a replication splitter, one or more local replication appliances, and one or more remote replication appliances connected to a remote data storage system configured as a destination. As a data storage system at a source processes IO requests specifying data to be written to a particular LUN, the replication splitter intercepts the IO requests and sends them to the local replication appliance (or appliances). The local replication appliance communicates with the remote replication appliance, and the two appliances orchestrate the storage of the data specified in the IO requests at the destination. In this manner, the destination is made to store a redundant copy of the data stored on the LUN, and the redundant copy may be used to recover the contents of the LUN in the event of a failure at the source.
A well-known solution for snapshot shipping replication is the Celerra Replicator™ V2, also available from EMC Corporation of Hopkinton, Mass. Replicator V2 includes software for performing replication on files and file systems. Replicator V2 operates by taking snaps (i.e., point in time copies) of files and file systems at a source, comparing current snaps with previous snaps, identifying differences, and sending the differences to a destination. The destination receives the differences and applies them to replicas maintained there, to update the replicas with changes made at the source.
Conventional replication may be synchronous or asynchronous. “Synchronous” replication proceeds in band with IO requests as the requests are processed at a source site. The source site typically sends data specified in individual IO requests to a destination site on an individual basis, e.g., one-by-one, as the IO requests are processed at the source. In contrast, “asynchronous” replication proceeds out of band with individual IO requests, with replicas generated, for example, on demand, at regular intervals, and/or in response to particular events. The above-described RecoverPoint system can perform both synchronous and asynchronous replication. The above-described Replicator V2 can perform asynchronous replication, as it operates based on snaps acquired out of band with IO processing.